initial import of py-fpconst-0.6.0

initial import of py-fpconst-0.6.0

This python module implements constants and functions for working with IEEE754
double-precision special values. It provides constants for Not-a-Number (NaN),
Positive Infinity (Inf), and Negative Infinity (-Inf), as well as functions to
test for these values.

The code is implemented in pure python by taking advantage of the 'struct'
standard module. Care has been taken to generate proper results on both
big-endian and little-endian machines. Some efficiency could be gained by
translating the core routines into C.